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package com.oracle.truffle.api.dsl.test.examples;

import com.oracle.truffle.api.Assumption;
import com.oracle.truffle.api.CallTarget;
import com.oracle.truffle.api.dsl.Cached;
import com.oracle.truffle.api.dsl.NodeChild;
import com.oracle.truffle.api.dsl.NodeChildren;
import com.oracle.truffle.api.dsl.Specialization;
import com.oracle.truffle.api.nodes.DirectCallNode;
import com.oracle.truffle.api.nodes.IndirectCallNode;
import com.oracle.truffle.api.utilities.CyclicAssumption;

/**
 * This example is based on the SLDispatchNode of SimpleLanguage. It shows how to implement a simple
 * inline cache with an assumption that needs to be checked.
 *
 * Note that if an assumption is invalidated the specialization instantiation is removed.
 */
@SuppressWarnings("unused")
@NodeChildren({@NodeChild("function"), @NodeChild("arguments")})
public class StableDispatch {

    public static class StableDispatchNode extends ExampleNode {

        @Specialization(guards = "function == cachedFunction", assumptions = "cachedFunction.getCallTargetStable()", limit = "3")
        protected static Object directDispatch(SLFunction function, Object[] arguments, //
                        @Cached("function") SLFunction cachedFunction, //
                        @Cached("create(cachedFunction.getCallTarget())") DirectCallNode callNode) {
            return callNode.call(arguments);
        }

        @Specialization(replaces = "directDispatch")
        protected static Object indirectDispatch(SLFunction function, Object[] arguments, //
                        @Cached IndirectCallNode callNode) {
            return callNode.call(function.getCallTarget(), arguments);
        }
    }

    public static final class SLFunction {

        private CallTarget callTarget;
        private final CyclicAssumption callTargetStable;

        protected SLFunction(String name) {
            this.callTargetStable = new CyclicAssumption(name);
        }

        protected void setCallTarget(CallTarget callTarget) {
            this.callTarget = callTarget;
            this.callTargetStable.invalidate();
        }

        public CallTarget getCallTarget() {
            return callTarget;
        }

        public Assumption getCallTargetStable() {
            return callTargetStable.getAssumption();
        }
    }

}
